When Israel’s Beresheet spacecraft launched toward the moon last week, it was carrying a mysterious cargo. Mission planners called it a time capsule but hinted that that wasn’t the whole story. Now the truth is out: The little lunar probe carries a 30-million-page archive of human knowledge etched into a DVD-size metal disc.

The Lunar Library, as the archive is known, constitutes a “civilization backup” to help ensure that our distant descendants never lose humanity's collective wisdom, according to Nova Spivack, co-founder of Arch Mission Foundation, the Los Angeles-based nonprofit behind the project. The foundation is building a space-based archive designed to survive for 6 billion years or more — a million times longer than the oldest written records in existence today.

“One of the primary evolutionary challenges that we face is amnesia about our past mistakes, and the lack of active countermeasures to repeating them,” Spivack said in an email. “For the survival of our species, we need to find ways to raise our awareness of what worked and didn't work, and we need to ensure it is shared with the people of the future.”

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Paul Davies, director of the Beyond Center for Fundamental Concepts in Physics at Arizona State University, regards the Lunar Library as mostly symbolic, yet still important. “It encourages people to reflect on humankind's place in the universe,” he said, and to rethink how we search for evidence of nonhuman civilizations, too.

“If we can leave records on the moon for a huge duration, maybe E.T. will have done the same,” Davies said, adding that it might make sense for humans to look for alien artifacts on the moon or other locations.

The world in a disc

Sending a library into space isn’t entirely new for the Arch Foundation. Before Elon Musk launched a Tesla Roadster into orbit around the sun last year, Spivack and his team put in its glove box a quartz disc containing the entire text of Asimov’s famous “Foundation” trilogy of science-fiction books, a major influence on Spivack’s thinking.

For the Lunar Library, the scope had to be far wider. “We are building a Rosetta Stone for beings who inhabit our solar system in the future,” Spivack said.

One small component of the archive is the time capsule Beresheet’s creators alluded to: a collection of songs, children’s drawings and writings about Israeli culture and history. But the rest is truly encyclopedic. Included in the Lunar Library’s more than 200 gigabytes of data are the entire English-language version of Wikipedia; tens of thousands of fiction and nonfiction books; a collection of textbooks; and a guide to 5,000 languages along with 1.5 billion sample translations between them.

All of that information is etched onto 25 stacked nickel disks, each just 40 microns (about 1/600th of an inch) thick.

Since people of the far future will presumably not have a DVD player handy, and might not speak any language now in use, the top of the Lunar Library’s disc is engraved with tiny images of books and other documents explaining human linguistics, along with instructions about how to read the library beneath. The introductory layers can easily be viewed when magnified 100 times under a simple microscope. Then it’s up to our crafty descendants to build the player so they can read the rest of the Library.

Built to last (almost) forever

All of that content will mean nothing if the physical object doesn’t survive, so the Arch Foundation helped develop a super-durable data-recording technology called Nanofiche for the Lunar Library disc. “It can withstand sustained heat that is 10 times greater than what is experienced on the moon with no damage to the data,” Spivack said of the disc, which is made of nickel because of its extreme durability and modest cost.

The Lunar Library is shielded by a protective layer and insulation, as well as the structure of the Beresheet lander itself. All of that should help safeguard it from micrometeorites that strike the moon on a regular basis. Even so, it may not have anything like the 6-billion-year lifetime that Spivack is targeting. “These objects will not survive for a billion years un-degraded, but they might be intact and unburied after 10 million years, maybe 50 million years,” Davies said.

Spivack acknowledged as much but pointed out that the Lunar Library is just one component of an even more audacious project called the Billion Year Archive — an effort that should live up to its name. The disc in the spacefaring Tesla is a test run of that archive, as is a prototype Arch Library launched into Earth's orbit last October. Many more collections are yet to come, each replicating the content in the Lunar Library.

“We want the archive to last longer than the moon itself,” he said. “If we place enough copies in enough places, some will make it into the distant future, no matter what happens on Earth, the moon, Mars or any other location.”

Now entering the age of immortality

The beginnings of the far-flung space library Spivack envisions are already out there, of course, starting with the cosmic maps aboard NASA’s Pioneer 10 and 11 spacecraft and the Golden Record affixed to the Voyager probes in the 1970s.

Spivack’s goal is to flood the solar system with other versions of the Lunar Library: in caves and mountains on Earth, on other locations on the moon, on Mars and in deep space. The Beresheet craft recently hit a glitch that has delayed its journey to the moon, but Spivack isn’t worried. Even if Beresheet fails, the Arch Foundation is already in discussions with other organizations about their upcoming space missions, including a lunar landing planned by the company Astrobotic.

Spivack can only speculate about what lessons far-future humans will need to relearn when they recover the libraries, and what kind of crises the knowledge in the Lunar Library might help avert. But he sees the benefits of his project already.

“By placing an archive of every past and present civilization on the moon, we can now say that civilization itself is on the moon,” he said. I want everyone to be able to look up at the moon and realize that humanity is now multiplanetary. This is a small shift in perspective with profound implications.”